Generally, an obstacle discrimination device can be mounted at a bumper of a vehicle. When an obstacle collides with the vehicle, the obstacle discrimination device discriminates whether or not the obstacle is a pedestrian. In the case where it is determined that the obstacle is the pedestrian, a pedestrian protecting device (e.g., active hood and cowl airbag) will be activated to protect the pedestrian.
That is, in the case where the obstacle colliding with the vehicle is not the pedestrian and the pedestrian protecting device (e.g., active hood) at the hood of the vehicle is activated, a variety of ill effects will be caused. For example, if a low-mass obstacle such as a triangle cone or a construction billboard colliding with the vehicle cannot be discriminated from a human (pedestrian), the pedestrian protecting device will be unnecessarily activated so that a redundant repair cost is caused. Moreover, if a weight obstacle (e.g., concrete wall and other vehicle) colliding with the vehicle cannot be distinguished from the human, the vehicle will be backed with the hood thereof being lifted so that the hood may penetrate into a passenger compartment. Thus, passengers in the vehicle are periled. Therefore, it is required to appropriately distinguish whether or not the obstacle is a pedestrian, for example, referring to JP-11-028994A and JP-11-310095A.
As described in JP-11-028994A, the pedestrian is distinguished based on a continuation time when a collision load (or deformation amount) exceeds a predetermined level. According to JP-11-310095A, the pedestrian is discriminated based on an increase rate of the collision load when the collision load exceeds a predetermined value. Moreover, referring to other art, the pedestrian is distinguished based on a peak value of the collision load.
That is, according to these related arts, the pedestrian is discriminated from other objects based on a predetermined variation component of a waveform of the collision load. In these cases, the collision load is to be corrected with respect to a velocity of the vehicle.
However, in these cases, it is necessary to mount at the vehicle bumper a load sensor for detecting the collision load exerted on the vehicle bumper by the collision obstacle, or a displacement sensor for detecting a deformation amount of the vehicle bumper, or a collision-detecting tube for detecting the collision load through a pressure variation. As a result, the mounting performance of the vehicle bumper, the bumper performance or the collision G-transmission capability for a passenger protection by an airbag will be deteriorated.